This invention relates generally to systems for storing liquids and more particularly to a petroleum storage structure utilizing earthen walls and floor for the major portion of the structure.
Conventional petroleum storage usually involves fabricated metal storage tanks. Such storage of petroleum is feasible where the storage is relatively temporary such as where the petroleum stored is in transit either for refining or for distribution by tanker, barge or ground transport.
Since the "Energy Crisis" incurred by the producing countries' oil boycott of 1974, there has been substantial concern that future crises will be precipitated by similar boycotts by oil producing nations. To avoid this President Ford has required that a substantial amount of crude oil be placed in storage in this country. This requirement has imposed a great deal of pressure to develop suitable storage capability for this inventory of petroleum. Among the suggested storage receivers are the salt domes which occur in certain parts of the country. The salt domes, although more economical then fabricated tanks, do have limitations in that their availability is restricted to certain geographical locations and do impose some pumping costs for injecting and recovering the petroleum from the formations.
Ground storage systems of the type of this invention have been generally described in the prior art, such, for example, as in the patents to Fish (U.S. Pat. No. 3,516,568), Prins (U.S. Pat. No. 3,052,380) and Webb (3,537,267); however, there are certain limitations in the prior art devices which are overcome by the present invention. A prime distinction of the present invention overcoming shortcomings of the prior art devices lies in the fact that petroleum is less dense than water. In a system where water encloses a petroleum product, as in the aforedescribed systems, the free surface of the water will be below that of the free surface of the petroleum. Utilizing a flexible liner between the water and the petroleum results in a differential unsupported area of contained petroleum. The lighter petroleum will also tend to spread as it is "buoyed" up by the water, thereby tending to spread the flexible liner radially, thereby bringing that liner into contact with the surface of the containing system. These problems are not dealt with in Fish; however, part of the problem is dealt with in Webb by utilizing containing liquids of different densities to compensate for the differential level. A liquid different than water to obtain this different density would be considered a pollutant in itself in that if it escaped into the ground water of the surrounding terrain, it would be an unnatural and therefore polluting substance thereby obviating one of the purposes of the invention.
The present invention overcomes this disadvantage by providing a three-phase system comprising petroleum enclosed in a flexible liner, a water jacket surrounding the bottom and sides of the petroleum, means to maintain the liner spaced from the water jacket container, and means to apply a load to the top surface of the petroleum to equalize the heights of the surface of the petroleum and the surrounding water.